Manila Bay island-building to sink inland homes – expert

Huge obstacles deter President Rody Duterte’s Great Manila Bay Rehab. Thirty-eight reclamations totaling 26,234 hectares are planned along almost the entire coastline. Environment lawyer Tony Oposa prefers calling the near-shore schemes “tambak” or landfilling. For, those are virtually island constructions for eventual high-rises. “The Bay is a nearly enclosed water body,” he says. “If islands are piled all over, then water flow all the more would be blocked, and waste and stink kept bayside.”

The island-building contradicts the Supreme Court order to clean up the Bay, that Oposa and 14 youths fought for starting 1999 – for future generations. Obstructed too is the Executive’s order for 178 cities and municipalities, and 5,714 barangays along the Bay and its inland tributaries in Metro Manila, Calabarzon, and Central Luzon to join in.

It defies science. About this time two years ago I wrote about the damage that Manila Bay reclamations would wreak. Not only coastal communities would be prone to storm surges. Those many kilometers inland also could be flooded. Liquefaction can sink the artificial islands during earthquakes. All those were from Dr. Kelvin S. Rodolfo’s 2015 study “On Geological Hazards that Threaten Existing and Proposed Reclamations of Manila Bay.” Rodolfo is professor emeritus of Earth and Environmental Sciences, University of Illinois at Chicago. The following year he presented a visual abridged version, “Dangerous Aspects of Reclamations along Manila Bay,” before the National Academy of Science and Technology. Both articles are online.

* * * Excerpts from my column of Mar. 13, 2017:

Four of 38 reclamations are about to commence: two in Manila, one in Pasay, and one in Cavite. The new real estate would bring mega-profits to the proponents. But wait, warns the Philippine government’s “Balik-Scientist” Kelvin Rodolfo. Millions of residents in Metro Manila, Bataan, Pampanga, Bulacan, and Cavite would be left in misery. Three disasters loom: • Seawater will flood coastal communities.

Due to sea temperature warming, sea levels are rising, especially near the equator. In the Philippines the rate of rise is as much as 14.7 mm a year, or above an adult’s ankle in ten years. At the same time, the Bay area is fast sinking. Unbridled extraction of groundwater is causing the surface to subside. The rate of subsidence in Greater Manila is about 19.2 mm a year, or deeper than an adult’s mid-leg in ten years. (Rodolfo likens that subsidence to the sinking of California’s San Joaquin Valley by eight meters, or a three-story house, due to groundwater overuse in the 1920s to 1970s.)

Manila Bay coastal plains slope up inland very gently. Ten to 20 km of land from the shore are only one meter above sea level. The combination of rising sea levels and land subsidence would make seawaters advance inland. Large swaths of the Bay area perpetually would be in knee-deep seawater in ten years.

Reclamations, being soft earth, would be susceptible to the combination of rising sea levels and subsidence. They would even hasten and deepen the flooding in other parts of the Bay area, as natural outflows of rivers and high tides would be clogged. Rodolfo cites the experience of Dagat-Dagatan in Navotas, Metro Manila. Starting in the 1970s the government poured billions of pesos for landfill and dikes – all for naught. Today more areas of the city are flooded than before.

• Storm surges would lash the coastal communities.

Typhoons are becoming stronger than ever due to climate change. Most at risk from storm surges and giant waves are coastal plains that slope up very gradually, like the Manila Bay area. History has shown evidence of typhoon destruction. Ships have been unchained from anchors and crashed against each other or onto Roxas Boulevard due to strong waves. Reclamations artificially would change the coastal contour, making them prone to storm surges and destructive waves.

• Liquefaction would sink coastal areas into the water in case of earthquake.

Liquefaction is when loose, saturated soil and sediments lose cohesion and temporarily behave like liquid. That’s what happened when buildings in downtown Dagupan City, beside Lingayen Gulf, sank as deep as one meter from the 1990 Luzon earthquake. Yet the epicenter was one hundred kilometers to the east, near Cabanatuan. In case the Big One strikes when Greater Manila’s West Valley Fault moves, reclaimed areas could suffer liquefaction. Structures could collapse.

Rodolfo warns against the reclamation of Sangley Point in Cavite, at the southern tip of Manila Bay, for a new airport. Such earth-filling could sink large parts of the heavily populated urbanized province due to hastened seawater rise, land subsidence, storm surges and waves, and earthquake liquefaction. Rodolfo cites Japan’s engineering fiasco at Kansai Airport, built on a reclaimed island off the bay coast of Osaka. More than $20 billion – 40-percent overbudget – was spent to reclaim land from the sea, pave two runways, build the terminals – and trying to outpace the sinking. Still it sunk, by 11.9 meters, or a four-story building. Ten percent of the cost went to waterproofing alone to save basements. The island continues to sink to this day. “Charot” is a Filipino colloquialism to mean “just kidding”. It masks the intentionally tart or unintentionally hurtful remark, turns the serious into joke, and exudes non-confrontation.

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